11 Digital Representations of Geographies: Geographical Look-Up-Tables
We`ve seen that there are different types of geography in use within the UK and that these geographies can be represented as digital boundaries. If you were to take 2 or more digital boundaries and overlay them in a GIS you would be able to look at the geographic regions in one type of geography and see which regions these are related to in a different type of geography. These relationships between different geographies can be encoded within a geographical lookup table. Geographical look up tables are very useful. If you have data at one geography but you need to perform analyse at another type of geography for which you have other data that you want to compare against then a geographical lookup table can be used to map one type of geography to another.
There are many geographical lookup tables available. One of the most important in the context of the ESRC Census Programme are postcode directories. These datasets provide a lookup between postcodes and a number of different types of geography, census included. To understand how postcode directories work take a look at the following interactive element:
A portion of the National Statistics Postcode Directory (NSPD) is shown below:"
Here PCD is postcode OSLAUA is County/Council Area DZONE1 is Datazone OSWARD is Electoral Ward PCON is Parliamentary Constituency